Mixture between the SSD and HSD hypothesis in 2νββ decay

This paper delves into the calculation of nuclear matrix elements for the two-neutrino double-beta (2νββ ) decay, aiming to provide fresh insights. A novel toy model is introduced, merging the single state dominance (SSD) and higher state dominance (HSD) hypotheses. Drawing from the recent measurement of the shape factor ξ312v, our toy model anticipates a scenario of destructive mixing between the SSD and HSD states in the context of 2νββ decay of 100Mo. This finding is in accordance with our proton neutron quasi-random phase approximation (pn-QRPA) calculations, which also indicates cancellations between contributions from low-lying and higher-lying states.